1. Technical Field
The present invention relates to a robot control system, a robot system, a sensor information processing apparatus, and the like.
2. Related Art
As work performed using a robot such as a manipulator, there is work involving various constraint conditions such as contact with an object. In such a case, in addition to position control, force control is often required. For example, when the surface of an object is traced, when one object is fitted in another object, or when a soft object is gripped not to be broken, a motion corresponding to reaction from the object is necessary in addition to simple position control.
As a representative method for performing force control in a robot, there is a method called impedance control. The impedance control is a control method for causing a robot to act, irrespective of the actual mass, the viscosity characteristic, and the elasticity characteristic of the robot, as if the robot has values of the actual mass, the viscosity characteristic, and the elasticity characteristic suitable for work. This is a control method for solving an equation of motion on the basis of force information obtained from a force sensor or the like attached to the robot and causing the robot to act according to the solution. By appropriately setting the equation of motion, it is possible to cause the robot such as the manipulator to act as if the robot has predetermined mass, viscosity, and elasticity. As related arts concerning such impedance control and force control, techniques disclosed in JP-A-6-320451 (Patent Literature 1), JP-A-2-205489 (Patent Literature 2), and JP-A-4-369004 (Patent Literature 3) are known.
Patent Literature 1 discloses a method of accurately performing the impedance control even in an extremely complicated system, for example, when a control target is soft.
Patent Literature 2 discloses a method of providing a motion model on the inside of a control system to thereby, estimate force and performing the impedance control while making it unnecessary to use a sensor, although the control system is complicated, and using a simpler mechanical structure.
On the other hand, Patent Literature 3 discloses one method for reducing a calculation amount. This is a method of reducing a calculation amount by using a transpose Jacobian matrix without performing calculation for calculating an inverse Jacobian matrix described in Patent Literatures 1 and 2. In the impedance control, in order to cause the robot or the like to behave as if the robot has desired characteristics (mass, viscosity characteristic, and elasticity characteristic), it is necessary to solve an ordinary differential equation (a motion equation serving as a secondary linear ordinary differential equation) in which coefficient parameters corresponding to the characteristics are used. Various methods of solving the ordinary differential equation are known. However, the Runge-Kutta method, the Newton method, or the like are used.
However, these methods are not suitable for hardwaring. Determination of stability is difficult with these methods. Further, it is difficult to cope with switching of responsiveness. The responsiveness means a dynamic characteristic determined by the desired characteristics (mass, viscosity characteristic, and elasticity characteristic) given to the robot. Low responsiveness indicates, for example, characteristics realized by a large mass coefficient, a large viscosity coefficient, and a small elasticity coefficient. High responsiveness indicates, for example, characteristics realized by a small mass coefficient, a small viscosity coefficient, and a large elasticity coefficient. Optimum characteristics of these characteristics vary depending on realized work content or a scene of work. Therefore, it is an extremely important function to be capable of easily switching response characteristics.